The du command can be used in any Unix shell to determine how much space a folder is taking. It’s a quick way to determine which directory is using the most space.

If you run du on the root drive “/” then you will get an idea of how much space the drive is using. One unfortunate side effect of that command is if you have any mounted drives or other filesystems, it will search the disk usage of those folders as well. Aside from taking a long time that method provides data we don’t necessarily want.

Fortunately, there are a few switches you can use to fix this problem. The -x switch tells du to ignore other filesystems. Perfect.

There are a few other switches that prove useful. Below is a list of my favorites:

• -x Ignore other filesystems
• -h Use human readable numbers (kilobytes, megabytes, and gigabytes) instead of raw bytes
• -s Provide a summary of the folder instead of listing the size of each file inside the folder
• * (not a switch, but rather an argument to put after your directory.) This summarizes subfolders in that directory, as opposed to simply returning the size of that directory.

For troubleshooting low disk space errors, the following command will give you a good place to start:

du -hsx /*

You can then dig further by altering the above command to reflect a directory instead of /, or simply do * if you want a breakdown of the directory you are currently in.